1. Field of the Invention
This invention relates to a traveling seat and more particularly relates to a traveling seat especially for physically handicapped persons having a frame fastened to a seat shell.
2. Description of Related Art
Traveling seats used for transporting individuals are known. For example, strollers may be used to transport small children. In this case, a frame has a bar located approximately 1.20 m above the surface on which the wheels of the frame stand. The bar may be grasped by a person to move the stroller. Depending on the type of the stroller, it may be equipped with three or four wheels, with one or two of said wheels being articulated in a steerable manner to the frame.
Another type of traveling seat is a wheelchair. In contrast to a stroller, a wheelchair tends to have larger rear wheels that can be operated by hand by the person seated in the wheelchair. However, some wheelchairs may be equipped only with small wheels, thus requiring a care giver to push them using handles or a bar mounted at a suitable height.
Some types of seats, such as those used for strollers, include a seat shell with a backrest and footrest articulated to the seat surface. The seat back and footrest pivot relative to the seat surface and can be locked in certain positions, so that the posture of the person sitting on the seat shell can be varied from an upright position, with the upper body and knees bent, to a nearly straight lying position. Seat shells of this type are used, for example, for alternative mounting on a stroller or on a mounting device in an automobile, so that they can be used as child seats.
According to the present invention, the backrest and footrest are both coupled to the seat surface via a pivot. A tensioning device creates a tensioning force that disposes the seat surface, backrest and footrest in a configuration appropriate for sitting.
The seat according to the invention is especially provided to hold persons who suffer from spasms. In these patients, uncontrolled impulses are delivered to the muscles that result in a cramp-like tensing of the muscles which generally causes the body to stretch out. In other words, the seated person actuates his muscles in such fashion that the hip joints and knee joints are straightened. To prevent the patient from falling out of the seat shell of the seat, generally the patient is held on the seat shell by restraining means, comprising a lap belt or lap bar for example. In conventional seats, the patient is restrained in a rigid seat or seat shell that is adjustable and can be locked in position. During a spastic attack, the muscles exert forces on the restraining means which hold the joints of the patient in the bent position and secure the patient in the seated position. Because the tensing of the muscles cannot lead to a stretching of the body, the muscles and ligaments that bind the joints are subjected to high mechanical stress. In addition, the full muscular force is exerted on the fastening means and the seat shell resulting in considerable mechanical stress on these items.
The device described herein allows the back rest and seat surface to pivot when subjected to a muscular force. The footrest, too, can pivot into alignment with the seat surface. Thus, in spite of the restraining devices, the seat permits the body to straighten in response to tensing of the muscles. The mechanical stresses on the muscles and on the ligaments of the patient, as well as on the seat surface and the footrest are considerably reduced. Since the patient is also preferably restrained in the seat shell by at least one lap belt, it is not possible for the patient to fall out of the seat.
Tensioning devices produce a tensioning force that holds the seat shell and the footrest in the sitting position at least until the person to be accommodated is seated. Advantageously, a sufficiently high tensioning force may be produced to counteract the muscular force and to brake the stretching movement so that excessively rapid stretching of the body does not occur. As a result, the risk of injury to the seated person and of damage to the articulated connections on reaching their end stops is reduced.
A locking device may be provided that inhibits the pivoting of the seat shell and/or footrest when such pivoting is not desired. Such might be the case, for example, when a patient in a wheelchair is pushed into a cramped elevator where injury might result if seat parts were to pivot. In addition, the contact surface of the backrest may also be extended from the seat surface, parallel to the principal plane of the backrest, with a tensioning device again being provided that holds the contact surface in the position closest to the seat surface. During complete stretching of the patient""s body, the distance between the shoulder part and the point where the feet contact the footrest generally increases; the device described herein accounts for this, and allows the seat (e.g., as part of a wheelchair) to completely follow the stretching movement. A locking device can also be provided to inhibit motion of the backrest.
The tensioning devices are preferably constructed using tensioning springs. These springs may be designed as either tension springs or compression springs, depending on the articulation points for the tensioning springs. In some cases, coil springs made of steel may be used. Gas springs are also suitable for this application. Other tensioning devices are also possible, weights for example, that press the individual parts of the seat into the original bent sitting position by gravity.
The contact surface of the backrest, while remaining movable, may be connected directly to the lower part of the backrest so that the sliding guide for the contact surface is integrated into the backrest. Preferably, however, a sliding guide may be articulated to a rear strut of the frame in which the contact surface of the backrest is guided. This provides that even when the backrest pivots relative to the seat surface, the backrest is supported by the articulation point on the frame and hence the forces exerted by the weights and the muscular forces are reliably transmitted to the frame. The tensioning springs that form a pretensioning device for the movable contact surface may be integrated into the sliding guide. A sliding guide is preferably attached to the frame below the seat surface, with the seat surface being articulated to the movable part of the guide. A tensioning spring subjected to tension engages the movable part, said spring pulling the seat surface backward, i.e. toward the backrest, so that the seat surface and the backrest are pulled into the bent sitting position. It may be desirable to provide a stop for the pivoting movement of the elements of the seat shell and the footrest and for the translational motion of the contact surface of the backrest in order to prevent the parts from being moved excessively by muscular force, which could damage the tensioning devices or could allow the patient sitting on the seat to be injured.
The seat surface and the backrest of the seat shell may be made of load-carrying shell-like structures such as steel or plastic and may be provided with thick, comfortable cushions. In order to prevent the cushion from being jammed when the seat back is pivoted relative to the seat surface, a cover strip may be provided for covering the rear edge of the seat surface and the lower edge of the backrest. The cover strip may prevent the cushions mounted on the seat surface and the backrest from entering the above gap. Advantageously, the cover strip may be mounted in the vicinity of the two edges, i.e. the edges of the seat surface and the backrest, and may slide in the vicinity of the other edges.
Further advantages and features of the invention follow from the description of the drawings below and the claims.